Control mechanism for cam phaser

ABSTRACT

A VCT phaser having a mechanical feedback in which no elaborate sensors and its concomitant electronic control loop is required. The phaser has centerly mounted spool valve controlling the flow of control fluid such that when a command positions the same at a predetermined position, passages within the phaser adjusts to a desired position through the mechanical feedback.

REFERENCE TO PROVISIONAL APPLICATION

This application claims an invention which was disclosed in ProvisionalApplication No. 60/510,373, filed Oct. 10, 2003, entitled “CONTROLMECHANISM FOR CAM PHASER”. The benefit under 35 USC § 119(e) of theUnited States provisional application is hereby claimed, and theaforementioned application is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention pertains to the field of mechanical feedback. Moreparticularly, the invention pertains to control mechanism for a camphaser having a center mounted spool with two helical slots.

BACKGROUND OF THE INVENTION

The performance of an internal combustion engine can be improved by theuse of dual camshafts, one to operate the intake valves of the variouscylinders of the engine and the other to operate the exhaust valves.Typically, one of such camshafts is driven by the crankshaft of theengine, through a sprocket and chain drive or a belt drive, and theother of such camshafts is driven by the first, through a secondsprocket and chain drive or a second belt drive. Alternatively, both ofthe camshafts can be driven by a single crankshaft powered chain driveor belt drive. Engine performance in an engine with dual camshafts canbe further improved, in terms of idle quality, fuel economy, reducedemissions or increased torque, by changing the positional relationshipof one of the camshafts, usually the camshaft which operates the intakevalves of the engine, relative to the other camshaft and relative to thecrankshaft, to thereby vary the timing of the engine in terms of theoperation of intake valves relative to its exhaust valves or in terms ofthe operation of its valves relative to the position of the crankshaft.

Consideration of information disclosed by the following U.S. patents,which are all hereby incorporated by reference, is useful when exploringthe background of the present invention.

U.S. Pat. No. 5,002,023 describes a VCT system within the field of theinvention in which the system hydraulics includes a pair of oppositelyacting hydraulic cylinders with appropriate hydraulic flow elements toselectively transfer hydraulic fluid from one of the cylinders to theother, or vice versa, to thereby advance or retard the circumferentialposition on of a camshaft relative to a crankshaft. The control systemutilizes a control valve in which the exhaustion of hydraulic fluid fromone or another of the oppositely acting cylinders is permitted by movinga spool within the valve one way or another from its centered or nullposition. The movement of the spool occurs in response to an increase ordecrease in control hydraulic pressure, PC, on one end of the spool andthe relationship between the hydraulic force on such end and anoppositely direct mechanical force on the other end which results from acompression spring that acts thereon.

U.S. Pat. No. 5,107,804 describes an alternate type of VCT system withinthe field of the invention in which the system hydraulics include a vanehaving lobes within an enclosed housing which replace the oppositelyacting cylinders disclosed by the aforementioned U.S. Pat. No.5,002,023. The vane is oscillatable with respect to the housing, withappropriate hydraulic flow elements to transfer hydraulic fluid withinthe housing from one side of a lobe to the other, or vice versa, tothereby oscillate the vane with respect to the housing in one directionor the other, an action which is effective to advance or retard theposition of the camshaft relative to the crankshaft. The control systemof this VCT system is identical to that divulged in U.S. Pat. No.5,002,023, using the same type of spool valve responding to the sametype of forces acting thereon.

U.S. Pat. Nos. 5,172,659 and 5,184,578 both address the problems of theaforementioned types of VCT systems created by the attempt to balancethe hydraulic force exerted against one end of the spool and themechanical force exerted against the other end. The improved controlsystem disclosed in both U.S. Pat. Nos. 5,172,659 and 5,184,578 utilizeshydraulic force on both ends of the spool. The hydraulic force on oneend results from the directly applied hydraulic fluid from the engineoil gallery at full hydraulic pressure, P_(S). The hydraulic force onthe other end of the spool results from a hydraulic cylinder or otherforce multiplier which acts thereon in response to system hydraulicfluid at reduced pressure, P_(C), from a PWM solenoid. Because the forceat each of the opposed ends of the spool is hydraulic in origin, basedon the same hydraulic fluid, changes in pressure or viscosity of thehydraulic fluid will be self-negating, and will not affect the centeredor null position of the spool.

U.S. Pat. No. 5,289,805 provides an improved VCT method which utilizes ahydraulic PWM spool position control and an advanced control methodsuitable for computer implementation that yields a prescribed set pointtracking behavior with a high degree of robustness.

In U.S. Pat. No. 5,361,735, a camshaft has a vane secured to an end fornon-oscillating rotation. The camshaft also carries a timing belt drivenpulley which can rotate with the camshaft but which is oscillatable withrespect to the camshaft. The vane has opposed lobes which are receivedin opposed recesses, respectively, of the pulley. The camshaft tends tochange in reaction to torque pulses which it experiences during itsnormal operation and it is permitted to advance or retard by selectivelyblocking or permitting the flow of engine oil from the recesses bycontrolling the position of a spool within a valve body of a controlvalve in response to a signal from an engine control unit. The spool isurged in a given direction by rotary linear motion translating meanswhich is rotated by an electric motor, preferably of the stepper motortype.

U.S. Pat. No. 5,497,738 shows a control system which eliminates thehydraulic force on one end of a spool resulting from directly appliedhydraulic fluid from the engine oil gallery at full hydraulic pressure,P_(S), utilized by previous embodiments of the VCT system. The force onthe other end of the vented spool results from an electromechanicalactuator, preferably of the variable force solenoid type, which actsdirectly upon the vented spool in response to an electronic signalissued from an engine control unit (“ECU”) which monitors various engineparameters. The ECU receives signals from sensors corresponding tocamshaft and crankshaft positions and utilizes this information tocalculate a relative phase angle. A closed-loop feedback system whichcorrects for any phase angle error is preferably employed. The use of avariable force solenoid solves the problem of sluggish dynamic response.Such a device can be designed to be as fast as the mechanical responseof the spool valve, and certainly much faster than the conventional(fully hydraulic) differential pressure control system. The fasterresponse allows the use of increased closed-loop gain, making the systemless sensitive to component tolerances and operating environment.

U.S. Pat. No. 5,657,725 shows a control system which utilizes engine oilpressure for actuation. The system includes a camshaft that has a vanesecured to an end thereof for non-oscillating rotation therewith. Thecamshaft also carries a housing which can rotate with the camshaft butwhich is oscillatable with the camshaft. The vane has opposed lobeswhich are received in opposed recesses, respectively, of the housing.The recesses have greater circumferential extent than the lobes topermit the vane and housing to oscillate with respect to one another,and thereby permit the camshaft to change in phase relative to acrankshaft. The camshaft tends to change direction in reaction to engineoil pressure and/or camshaft torque pulses which it experiences duringits normal operation, and it is permitted to either advance or retard byselectively blocking or permitting the flow of engine oil through thereturn lines from the recesses by controlling the position of a spoolwithin a spool valve body in response to a signal indicative of anengine operating condition from an engine control unit. The spool isselectively positioned by controlling hydraulic loads on its opposed endin response to a signal from an engine control unit. The vane can bebiased to an extreme position to provide a counteractive force to aunidirectionally acting frictional torque experienced by the camshaftduring rotation.

U.S. Pat. No. 6,247,434 shows a multi-position variable camshaft timingsystem actuated by engine oil. Within the system, a hub is secured to acamshaft for rotation synchronous with the camshaft. A housingcircumscribes the hub and is rotatable with the hub and the camshaft andis further oscillatable with respect to the hub and the camshaft withina predetermined angle of rotation. Driving vanes are radially disposedwithin the housing and cooperate with an external surface on the hub,while driven vanes are radially disposed in the hub and cooperate withan internal surface of the housing. A locking device, reactive to oilpressure, prevents relative motion between the housing and the hub. Acontrolling device controls the oscillation of the housing relative tothe hub.

U.S. Pat. No. 6,250,265 shows a variable valve timing system withactuator locking for an internal combustion engine. The systemcomprising a variable camshaft timing system that includes a camshaftwith a vane secured to the camshaft for rotation with the camshaft butnot for oscillation with respect to the camshaft. The vane has acircumferentially extending plurality of lobes projecting radiallyoutwardly therefrom and is surrounded by an annular housing that has acorresponding plurality of recesses. Each of recesses receives one ofthe lobes and has a circumferential extent greater than thecircumferential extent of the lobe received therein to permitoscillation of the housing relative to the vane and the camshaft whilethe housing rotates with the camshaft and the vane. Oscillation of thehousing relative to the vane and the camshaft is actuated by pressurizedengine oil in each of the recesses on opposed sides of the lobe therein,the oil pressure in such recess being preferably derived in part from atorque pulse in the camshaft as it rotates during its operation. Anannular locking plate is positioned coaxially with the camshaft and theannular housing and is moveable relative to the annular housing along alongitudinal central axis of the camshaft between a first position,where the locking plate engages the annular housing to prevent itscircumferential movement relative to the vane and a second positionwhere circumferential movement of the annular housing relative to thevane is permitted. The locking plate is biased by a spring toward itsfirst position and is urged away from its first position toward itssecond position by engine oil pressure, to which it is exposed by apassage leading through the camshaft, when engine oil pressure issufficiently high to overcome the spring biasing force, which is theonly time when it is desired to change the relative positions of theannular housing and the vane. The movement of the locking plate iscontrolled by an engine electronic control unit either through a closedloop control system or an open loop control system.

U.S. Pat. No. 6,263,846 discloses a control valve strategy for vane-typevariable camshaft timing system. The strategy involves an internalcombustion engine that includes a camshaft and hub secured to thecamshaft for rotation therewith, where a housing circumscribes the huband is rotatable with the hub and the camshaft, and is furtheroscillatable with respect to the hub and camshaft. Driving vanes areradially inwardly disposed in the housing and cooperate with the hub,while driven vanes are radially outwardly disposed in the hub tocooperate with the housing and also circumferentially alternate with thedriving vanes to define circumferentially alternating advance and retardchambers. A configuration for controlling the oscillation of the housingrelative to the hub includes an electronic engine control unit, and anadvancing control valve that is responsive to the electronic enginecontrol unit and that regulates engine oil pressure to and from theadvance chambers. A retarding control valve responsive to the electronicengine control unit regulates engine oil pressure to and from the retardchambers. An advancing passage communicates engine oil pressure betweenthe advancing control valve and the advance chambers, while a retardingpassage communicates engine oil pressure between the retarding controlvalve and the retard chambers.

U.S. Pat. No. 6,311,655 shows multi-position variable cam timing systemhaving a vane-mounted locking-piston device. An internal combustionengine having a camshaft and variable camshaft timing system, wherein arotor is secured to the camshaft and is rotatable but non-oscillatablewith respect to the camshaft is discribed. A housing circumscribes therotor, is rotatable with both the rotor and the camshaft, and is furtheroscillatable with respect to both the rotor and the camshaft between afully retarded position and a fully advanced position. A lockingconfiguration prevents relative motion between the rotor and thehousing, and is mounted within either the rotor or the housing, and isrespectively and releasably engageable with the other of either therotor and the housing in the fully retarded position, the fully advancedposition, and in positions therebetween. The locking device includes alocking piston having keys terminating one end thereof, and serrationsmounted opposite the keys on the locking piston for interlocking therotor to the housing. A controlling configuration controls oscillationof the rotor relative to the housing.

U.S. Pat. No. 6,374,787 shows a multi-position variable camshaft timingsystem actuated by engine oil pressure. A hub is secured to a camshaftfor rotation synchronous with the camshaft, and a housing circumscribesthe hub and is rotatable with the hub and the camshaft and is furtheroscillatable with respect to the hub and the camshaft within apredetermined angle of rotation. Driving vanes are radially disposedwithin the housing and cooperate with an external surface on the hub,while driven vanes are radially disposed in the hub and cooperate withan internal surface of the housing. A locking device, reactive to oilpressure, prevents relative motion between the housing and the hub. Acontrolling device controls the oscillation of the housing relative tothe hub.

U.S. Pat. No. 6,477,999 shows a camshaft that has a vane secured to anend thereof for non-oscillating rotation therewith. The camshaft alsocarries a sprocket that can rotate with the camshaft but is oscillatablewith respect to the camshaft. The vane has opposed lobes that arereceived in opposed recesses, respectively, of the sprocket. Therecesses have greater circumferential extent than the lobes to permitthe vane and sprocket to oscillate with respect to one another. Thecamshaft phase tends to change in reaction to pulses that it experiencesduring its normal operation, and it is permitted to change only in agiven direction, either to advance or retard, by selectively blocking orpermitting the flow of pressurized hydraulic fluid, preferably engineoil, from the recesses by controlling the position of a spool within avalve body of a control valve. The sprocket has a passage extendingtherethrough. The passage extends parallel to and is spaced from alongitudinal axis of rotation of the camshaft. A pin is slidable withinthe passage and is resiliently urged by a spring to a position where afree end of the pin projects beyond the passage. The vane carries aplate with a pocket, which is aligned with the passage in apredetermined sprocket to camshaft orientation. The pocket receiveshydraulic fluid, and when the fluid pressure is at its normal operatinglevel, there is sufficient pressure within the pocket to keep the freeend of the pin from entering the pocket. At low levels of hydraulicpressure, however, the free end of the pin enters the pocket and latchesthe camshaft and the sprocket together in a predetermined orientation.

U.S. Pat. No. 6,477,999 shows a line control arrangement includes avalve timing controller generating a predetermined valve timing variablecontrol signal according to an engine speed of a vehicle; and an oilcontrolling driver generating a rotational force in a predetermineddirection according to the valve timing variable control signal receivedfrom the valve timing controller to form a corresponding advance lineand a corresponding retard line. The line control arrangement for acontinuously variable valve timing system reduces noise generated byoperation of an oil controlling driver.

Furthermore, camshaft phaser is well known. However, known phasers aretypically controlled much differently. For example, U.S. Pat. No.5,507,245 by Melchior, has disclosed a mechanical feedback including oneof the driving and driven parts of the coupling is connected to acylinder and the other to a piston which delimit therebetween twoantagonistic chambers. The chambers have a substantially constantvolume, and are filled with a practically incompressible hydraulicliquid, and are interconnected through two unidirectional circuits whichhave opposite directions and each a substantially constant volume. Adistributing device is so arranged as to either bring into action one orthe other of the unidirectional circuits, or to neutralize both of them.

In addition, it is known to have an electronic feedback loop involvingsensors sensing the positions of shafts such as camshaft or crankshaftin a VCT system. For example, pulse wheels are rigidly affixed onto theshafts for the sensors sensing purposes. The sensed pulses are in turnprocessed into information wherein derived positional information of arotor or vane in relation to a housing is used to control a controlvalve (spool) which in turn is used to control a phase relationship.Typically, the spool valve comprises two lands thereon for stoppingfluid communications as desired.

SUMMARY OF THE INVENTION

In a VCT phaser, a mechanical feedback mechanism is provided for atleast one vane to oscillate within a cavity free from electronics suchas cam sensors.

In a VCT phaser comprising a housing and a rotor, the rotor having acontrol valve which is rigidly coupled to the housing.

The present invention provides a means to control a cam phaser. The camphaser may be either a cam torque actuated phaser (CTA), or a torqueactuated (TA) phaser or an oil pressure actuated phaser (OPA).

The present invention provides a center-mounted spool or control valve,which is located rotationally to a housing. The spool has two helicalslots which serve to regulate the flow to the advance and retardchambers. Axial displacement of the spool allows either the advance orretard chambers to communicate with a common chamber. This results inthe rotor displacing rotationally until the common chamber no longercommunicates with either the advance or retard chambers. At this point anew equilibrium in terms of rotational position for the rotor relativeto the housing/spool is reached. Displacements of the rotor from thenull position are counteracted by the common chamber communicating toeither the advance and retard chambers. Therefore the rotationalposition is directly related to the axial position of the center spool.

Accordingly, a phaser is provided, which includes a housing having atleast one cavity therein; a rotor having at least one vane oscillatingwithin the at least one cavity of the housing, the rotor being disposedto engage the housing, or rotate relative the housing, the cavity beingdivided into an advance chamber and a retard chamber by the at least onevane; and disposed to translationally move within an opening of therotor along a substantially straight line, the control valve having atleast two openings for selectively controlling fluid flow among a set ofpassages within the phaser for control fluid to occupy either theadvance chamber or the retard chamber; at the outer surface of thecontrol valve, a helical slot having at least one side, wherein anon-zero angle exists between the at least one side and thesubstantially straight line, the helical slot having an opening forfacilitating fluid flow between chambers; thereby as the control valvemoves along the substantially straight line the vane position within thecavity is controlled.

Accordingly, a method is provided which comprises the steps of:providing a housing having at least one cavity therein; providing arotor having at least one vane oscillating within the at least onecavity of the housing, the rotor being disposed to engage the housing,or rotate relative the housing, the cavity being divided into an advancechamber and a retard chamber by the at least one vane; providing acontrol valve disposed to translationally move within an opening of therotor along a substantially straight line, the control valve having atleast two openings for selectively controlling fluid flow among a set ofpassages within the phaser for control fluid to occupy either theadvance chamber or the retard chamber; at the outer surface of thecontrol valve, providing a helical slot having at least one side,wherein a non-zero angle exists between the at least one side and thesubstantially straight line, the helical slot having an opening forfacilitating fluid flow between chambers; and translationally moving thecontrol valve along the substantially straight line a predetermineddistance for controlling the position of the vane within the cavity ofthe housing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a phaser assembly of the present invention.

FIG. 2 shows a side view of the phaser of the present invention.

FIG. 3 shows a perspective view of the phaser of the present invention.

FIG. 4 shows a top view of the phaser of the present invention.

FIG. 5 shows a schematic of the present invention.

FIG. 5A shows a first detailed portion of FIG. 5.

FIG. 5B shows a second detailed portion of FIG. 5.

FIG. 6 shows an exemplified phaser of the present invention in a firstdynamic state.

FIG. 6A shows the shape or formation of helical slot (52) in a firstdynamic state.

FIG. 7 shows an exemplified phaser of the present invention in a seconddynamic state FIG. 7A shows the shape or formation of helical slot (52)in a second dynamic state.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This section includes the descriptions of the present inventionincluding the preferred embodiment of the present invention for theunderstanding of the same. It is noted that the embodiments are merelydescribing the invention. The claims section of the present inventiondefines the boundaries of the property right conferred by law.

Referring to FIG. 1-7, a phaser (10) assembly is shown in part. Phaser(10) comprises a sprocket (12), a rotor (14), a housing (16), a backplate (18), and a spool (20) or control valve. A pair of check valves(22) is provided (only one shown). Sprocket (12) comprises a teethstructure (24) circumferentially formed upon the circumference thereof.Sprocket (12) further comprises an inner portion (26) that issubstantially of cylindrical shape formed at the center of the same.Inner portion (26) comprises a center opening (28) forming a hollowcylinder at the center for accommodating spool (20). Sprocket (12) has akey (27) of an elongated shape that protrudes from inner portion (26)into center opening (28) for slidably engaging a notch (30) formedaxially on the circumference of spool (20). Sprocket (12) furtherincludes a set of inner openings (29) (only three shown) on innerportion (26) for accommodating the maintenance of a set of couplingelements to affix rotor (14) onto a third member such as a camshaft (notshown). Sprocket (12) further has a set of outer openings (51) (only sixshown) for affixing the same onto housing (16) and back plate (18).

Rotor (14) comprises a center opening sprocket (12) of a substantiallycylindrical shape disposed to allow for the axial movement of spool (20)in that spool (20) can slide axially along an axis (34). Furthermore,rotor (14) can rotate in relation to spool (20) by frictionally engagingan inner surface (32) with an outer surface of spool (20) along axis(34). Rotor (14) further comprises a first vane (36) and a second vane(38) with each vane formed diametrically opposing or relative to theother vane. Second vane (38) has an opening therein disposed forreceiving check valve (22).

Housing (16) encloses rotor (14). A pair of cavities (40) is formeddiametrically opposing each other for accommodating first vane (36) andsecond vane (38) to oscillate therein. Circumferentially betweencavities (40), housing (16) has a set of openings (42). Openings (42)have identical numbers as that of outer openings (51) on back plate(18). Housing (16) further has an inner bearing surface (46) for rotablycoupling with an outer surface (48) of rotor (14).

Back plate (18) has a center opening having a diameter that is less thanthe diameter of rotor (14) between the center thereof and outer surface(48) for contributing to the closure of a set of passages (86, 88) forfluid communication between chambers defined within cavities (40) anddelimited by first vane (36) or second vane (38). In other words, partof the back plate (18), along with portions of the rotor (14) formspassages (86, 88). Back plate (18) further has a set of openings (51)having identical numbers as that of opening (42) or outer openings (51).

Spool (20) comprises a pair of helical slot (52) (only one shown) whichserve to regulate the flow to the advance and retard chambers. Helicalslot (52) function as a conduit for the selective fluid communicationsbetween the chambers defined by cavities (40) and subdivided by firstvane (36) and second vane (38). Spool (20) is disposed to have anactuator (not shown) having a suitable force exerted upon a first endthereof, and an elastic member (also not shown) having a correspondingsuitable force exerted upon a second or opposite end in a known manner.

Referring specifically to FIG. 2, a side view of the assembled phaser(10) is shown. At the first end of phaser (10) along line axis (34), issprocket (12) with its teeth structure (24) and inner portion (26). Notethat teeth structure (24) is disposed to engage a chain such as anengine timing chain (not shown). Housing (16) is mounted onto sprocket(12). Typically, housing (16) is rigidly connected to sprocket (12) bysome connecting means such as screws. Portions of sprocket (12) form aside wall of cavities (40). Back plate (18) is mounted onto housing(16). Similarly, back plate (18) is rigidly connected to housing (16) bysome connecting means such as screws. Portions of back plate (18) alsoform a side wall of cavities (40).

Spool (20) is disposed at the center of phaser (10). Spool (20) cantranslationally move along axis (34). In addition, spool (20) cansimultaneously rotated with the inner bearing surfaces of rotor (14). Itshould be noted that spool (20) is connected to sprocket (12) by notch(30) and key (27). Therefore, spool (20) rotates in unison with sprocket(12) yet spool (20) can still translationaly slide along axis (34).

Referring specifically to FIG. 3, a perspective view of phaser (10) isshown. As can be seen, key (27) of inner portion (26) is connected tonotch (30) of spool (20), with spool (20) located within center opening(28) of inner portion (26). Through key (27) and notch (30), sprocket(12) and spool (20) are disposed to engage each other and rotate inunison together for a predetermined angular relationship betweensprocket (12) and rotor (14). As shown earlier, rotor (14) has an innerbearing surface which rotates with the outer bearing surface of spool(20). By way of an example, phaser (10) is a cam phaser mounted on oneend of a camshaft with rotor (14) rigidly affixed onto the one end.Spool (20) of sprocket (12) is coupled to a crankshaft by means of atiming chain. An angular adjustment can be achieved by relativemovements of sprocket (12) in relation to rotor (14). According to thepresent invention, the angular adjustment is accomplished by movingspool (20) translationally along axis (34) relatively to the othermembers of phaser (10). By positioning spool (20) at a plurality ofpredetermined positions along axis (34), a mechanical feedback orself-adjustment mechanism (details shown infra) adjusts the angularrelationship between the camshaft and the crankshaft.

Referring specifically to FIG. 4, an elevated perspective view of phaser(10) is shown. Note the inner openings (29) facilitate the three screws(54) going through rotor (14). It is noted that FIG. 4 merely shows aspecial case of the angular relationship between sprocket (12) and rotor(14), in which inner openings (29) of sprocket (12) happens to permit atop view of screws (54). Screws (54) are not affixed onto sprocket (12),but instead screws (54) are affixed onto rotor (14) which rotatesrelative to sprocket (12). Therefore, at other angular relationships,screws (54) may only be partially shown or not shown at all. Also notethe inner portion (26) of spool (20) located inside a cylindrical hollow(58) of spool (20). Further, the present figure shows another view ofkey (27) of sprocket (12) disposed to engage and rotate with spool (20)by way of key (27) engaging notch (30) of spool (20). In addition,opening (60) may be used to rigidly affix sprocket (12) onto housing(16).

Referring specifically to FIG. 5, a schematic depicting the presentinvention is provided. Cavities (40) each being subdivided into anadvance chamber A and a retard chamber R by first vane (36) andsimilarly subdivided by second vane (38) respectively. In addition, theadvance chamber A of one of the cavities (40) is coupled to and in fluidcommunication with the advance chamber A of the other cavities (40).Similarly, the retard chamber R of one of the cavities (40) is coupledto and in fluid communication with the retard chamber R of the othercavities (40). A third chamber or common passage (62) is formed withinrotor (14) having a first end (64) and a second end (66). First end (64)is always in fluid communication with a passage (68) in spool (20) viahelical slot (52). Second end (66) is formed as a result in which commonpassage (62) extends from rotor (14) toward second vane (38). A pair ofcheck valves (70) is provided to selectively permit control fluid toflow either to the advance chamber A of second vane (38), or the retardchamber R of second vane (38).

Retard chamber R of first vane (36) is deposed to be selectively coupledto the advance chamber of second vane (38) through passages andcontrolled by helical slot (52) of spool (20). Passage (74) isinterposed between retard chamber R of first vane (36) and helical slot(52) of spool (20). Similarly, advance chamber A of first vane (36) isdeposed to be selectively coupled to the retard chamber of second vane(38) through passage and controlled by helical slot (52) of spool (20).Passage (74) is interposed between advance chamber A of first vane (36)and helical slot (52) of spool (20). Preferably, when retard chamber Rof first vane (36) is selected to be in fluid communication with advancechamber of second vane (38) through passage and controlled by helicalslot (52) of spool (20), advance chamber A of first vane (36) is not influid communication with the retard chamber of second vane (38).

Symbol AB defines a region wherein detailed operation of the fluid flowis shown (see specifically FIGS. 5A and 5B). As spool (20) movestranslationaly along axle axis (34), helical slot (52) are formed suchthat control fluid from either advance chamber A of first vane (36) ispermitted to flow therefrom toward retard chamber R of second vane (38),or alternatively retard chamber R of first vane (36) is permitted toflow therefrom toward advance chamber A of second vane (38).

Referring specifically to FIG. 5A, a first detailed depiction of FIG. 5is shown. A first control fluid path (80) is formed which allows controlfluid to flow from passage (72) to passage (64) via passage (68) ofspool (20). No fluid flows out of passage (74) because the shape ofhelical slot (52) of spool (20) prevents any fluid flow therethrough.

Referring specifically to FIG. 5B, a second detailed depiction of FIG. 5is shown. A second control fluid path (82) is formed which allowscontrol fluid to flow from passage (74) to passage (64) via passage (68)of spool (20). No fluid flows out of passage (72) because the shape ofhelical slot (52) of spool (20) prevents any fluid flow therethrough.

A practical example of the present invention is shown in FIGS. 6-7A.Referring to FIG. 6, an exemplified phaser of the present invention in afirst dynamic state is shown. Housing (16) encloses sprocket (12) havingsecond vane (38) and first vane (36) each oscillating within cavities(40) respectively. Rotor (14) has first groove 86 facilitating fluidcommunication between the two retard chambers. Rotor (14) further has asecond groove 88 facilitating fluid communication between the twoadvance chambers. Spool (20) is disposed at the center of rotor (14).Due to the shape of helical slot (52) of spool (20), first end (64) ofrotor (14) is in constant fluid communication with passage (68) of spool(20) in its entire range of translational movement. Whereas, Due to theshape or formation of helical slot (52) of spool (20), passage (74) isin fluid communication with passage (68), but passage (72) of rotor (14)is not in communication with first end (64) due to the shape of helicalslot (52).

Referring to FIG. 6A, the shape or formation of helical slot (52) isshown. Helical slot (52) is a hollowed out portion or region of spool(20) thereon its outer surface. Helical slot (52) has six sides. Two ofthe six sides, specifically side (90) and side (92), possess a pair ofnon-zero angles in relation to the generally symmetrical shape of spool(20). In other words, angle θ₁ and angle θ₂ are of a non-zero value.Further, side (90) and side (92) are of a sufficient length to be atleast longer than the diameter of passage (72) or passage (74)respectively. It is noted or repeated herein that, unlike passage (68)which is part of or formed within spool (20), passage (72) and passage(74) are not part of spool (20) but a part of rotor (14) formeddiametrically at about opposite positions in a cylindrical hollow at thecenter thereof for accommodating spool (20). Helical slot (52) is formedso that either passage (68) and passage (74), or passage (68) andpassage (72) are respectively in fluid communication with each other.When spool (20) moves translationally back and forth along axis (34),either passage (68) and passage (74), or passage (68) and passage (72)are permitted to communicate. Therefore, fluid from either retardchamber flows toward advance chamber or vice versa. The result is thatrotor (14) rotates in relation to housing (16). The amount of movementor the duration spool (20) stays at a predetermined position in relationto rotor (14) determines the angle or phase of the rotation betweenrotor (14) and housing (16).

As can be seen, an actuator (not shown) acting upon one side of spool(20) and an elastic member (also not shown) reacting on the oppositeside of spool (20) can cause and adjust the movement or the durationspool (20) staying at the predetermined position in relation to rotor(14). Therefore, a controller (not shown) that controls the actuationand adjustment of the actuator can be used to predetermine the phaserelationship between rotor (14) and housing (16). Therefore, path (82)is active and path (80) is not.

Referring to FIG. 7, an exemplified phaser of the present invention in asecond dynamic state is shown. Housing (16) encloses sprocket (12)having second vane (38) and first vane (36) each oscillating withincavities (40) respectively. Rotor (14) has first groove 86 facilitatingfluid communication between the two retard chambers. Rotor (14) furtherhas a second groove 88 facilitating fluid communication between the twoadvance chambers. Spool (20) is disposed at the center of rotor (14).Due to the shape of helical slot (52) of spool (20), first end (64) ofrotor (14) is in constant fluid communication with passage (68) of spool(20) in its entire range of translational movement. Whereas, due to theshape or formation of helical slot (52) of spool (20), passage (74) isin fluid communication with passage (68), but passage (72) of rotor (14)is not in communication with first end (64) due to the shape of helicalslot (52). Therefore, path (80) is active and path (82) is not.

Referring to FIG. 7A, the shape or formation of helical slot (52) isshown. helical slot (52) is a hollowed out portion of spool (20) havingsix sides. Two of the six sides specifically side (90) and side (92)possess a pair of non-zero angles in relation to the generallysymmetrical shape of spool (20). In other words, angle θ₁ and angle θ₂are of a non-zero value. Further, side (90) and side (92) are of asufficient length to at least longer than the diameter of passage (72)or passage (74) respectively. It is noted or repeated herein that,unlike passage (68) which is part of or formed within spool (20),passage (72) and passage (74) is not part of spool (20) but a part ofrotor (14) formed diametrically at about opposite positions in acylindrical hollow at the center thereof for accommodating spool (20).Helical slot (52) is formed so that only passage (68) and passage (74),or passage (68) and passage (72) are respectively in fluidcommunication. When spool (20) moves translationally back and forthalong axis (34), either passage (68) and passage (74), or passage (68)and passage (72) are permitted to communicate. Therefore, fluid fromeither retard chamber flows toward advance chamber or vice versa. Theresult is that rotor (14) rotates in relation to housing (16). Theamount of movement or the duration spool (20) stays at a predeterminedposition in relation to rotor (14) determines the angle or phase of therotation between rotor (14) and housing (16).

As can be seen, an actuator (not shown) acting upon one side of spool(20) and an elastic member (also not shown) reacting on the oppositeside of spool (20) can cause and adjust the movement or the durationspool (20) staying at the predetermined position in relation to rotor(14). Therefore, a controller (not shown) that controls the actuationand adjustment of the actuator can be use to predetermine the phaserelationship between rotor (14) and housing (16).

The following are terms and concepts relating to the present invention.

It is noted the hydraulic fluid or fluid referred to supra are actuatingfluids. Actuating fluid is the fluid which moves the vanes in a vanephaser. Typically the actuating fluid includes engine oil, but could beseparate hydraulic fluid. The VCT system of the present invention may bea Cam Torque Actuated (CTA) VCT system in which a VCT system that usestorque reversals in camshaft caused by the forces of opening and closingengine valves to move the vane. The control valve in a CTA system allowsfluid flow from advance chamber to retard chamber, allowing vane tomove, or stops flow, locking vane in position. The CTA phaser may alsohave oil input to make up for losses due to leakage, but does not useengine oil pressure to move phaser. Vane is a radial element actuatingfluid acts upon, housed in chamber. A vane phaser is a phaser which isactuated by vanes moving in chambers.

There may be one or more camshaft per engine. The camshaft may be drivenby a belt or chain or gears or another camshaft. Lobes may exist oncamshaft to push on valves. In a multiple camshaft engine, most oftenhas one shaft for exhaust valves, one shaft for intake valves. A “V”type engine usually has two camshafts (one for each bank) or four(intake and exhaust for each bank).

Chamber is defined as a space within which vane rotates. Chamber may bedivided into advance chamber (makes valves open sooner relative tocrankshaft) and retard chamber (makes valves open later relative tocrankshaft). Check valve is defined as a valve which permits fluid flowin only one direction. A closed loop is defined as a control systemwhich changes one characteristic in response to another, then checks tosee if the change was made correctly and adjusts the action to achievethe desired result (e.g. moves a valve to change phaser position inresponse to a command from the ECU, then checks the actual phaserposition and moves valve again to correct position). Control valve is avalve which controls flow of fluid to phaser. The control valve mayexist within the phaser in CTA system. Control valve may be actuated byoil pressure or solenoid. Crankshaft takes power from pistons and drivestransmission and camshaft. Spool valve is defined as the control valveof spool type. Typically the spool rides in bore, connects one passageto another. Most often the spool is located on center axis of rotor of aphaser.

Differential Pressure Control System (DPCS) is a system for moving aspool valve, which uses actuating fluid pressure on each end of thespool. One end of the spool is larger than the other, and fluid on thatend is controlled (usually by a Pulse Width Modulated (PWM) valve on theoil pressure), full supply pressure is supplied to the other end of thespool (hence differential pressure). Valve Control Unit (VCU) is acontrol circuitry for controlling the VCT system. Typically the VCU actsin response to commands from ECU.

Driven shaft is any shaft which receives power (in VCT, most oftencamshaft). Driving shaft is any shaft which supplies power (in VCT, mostoften crankshaft, but could drive one camshaft from another camshaft).ECU is Engine Control Unit that is the car's computer. Engine Oil is theoil used to lubricate engine, pressure can be tapped to actuate phaserthrough control valve.

Housing is defined as the outer part of phaser with chambers. Theoutside of housing can be pulley (for timing belt), sprocket (for timingchain) or gear (for timing gear). Hydraulic fluid is any special kind ofoil used in hydraulic cylinders, similar to brake fluid or powersteering fluid. Hydraulic fluid is not necessarily the same as engineoil. Typically the present invention uses “actuating fluid”. Lock pin isdisposed to lock a phaser in position. Usually lock pin is used when oilpressure is too low to hold phaser, as during engine start or shutdown.

Oil Pressure Actuated (OPA) VCT system uses a conventional phaser, whereengine oil pressure is applied to one side of the vane or the other tomove the vane.

Open loop is used in a control system which changes one characteristicin response to another (say, moves a valve in response to a command fromthe ECU) without feedback to confirm the action.

Phase is defined as the relative angular position of camshaft andcrankshaft (or camshaft and another camshaft, if phaser is driven byanother cam). A phaser is defined as the entire part which mounts tocam. The phaser is typically made up of rotor and housing and possiblyspool valve and check valves. A piston phaser is a phaser actuated bypistons in cylinders of an internal combustion engine. Rotor is theinner part of the phaser, which is attached to a camshaft.

Pulse-width Modulation (PWM) provides a varying force or pressure bychanging the timing of on/off pulses of current or fluid pressure.Solenoid is an electrical actuator which uses electrical current flowingin coil to move a mechanical arm. Variable force solenoid (VFS) is asolenoid whose actuating force can be varied, usually by PWM of supplycurrent. VFS is opposed to an on/off (all or nothing) solenoid.

Sprocket is a member used with chains such as engine timing chains.Timing is defined as the relationship between the time a piston reachesa defined position (usually top dead center (TDC)) and the timesomething else happens. For example, in VCT or VVT systems, timingusually relates to when a valve opens or closes. Ignition timing relatesto when the spark plug fires.

Torsion Assist (TA) or Torque Assisted phaser is a variation on the OPAphaser, which adds a check valve in the oil supply line (i.e. a singlecheck valve embodiment) or a check valve in the supply line to eachchamber (i.e. two check valve embodiment). The check valve blocks oilpressure pulses due to torque reversals from propagating back into theoil system, and stop the vane from moving backward due to torquereversals. In the TA system, motion of the vane due to forward torqueeffects is permitted; hence the expression “torsion assist” is used.Graph of vane movement is step function.

VCT system includes a phaser, control valve(s), control valveactuator(s) and control circuitry. Variable Cam Timing (VCT) is aprocess, not a thing, that refers to controlling and/or varying theangular relationship (phase) between one or more camshafts, which drivethe engine's intake and/or exhaust valves. The angular relationship alsoincludes phase relationship between cam and the crankshafts, in whichthe crankshaft is connected to the pistons.

Variable Valve Timing (VVT) is any process which changes the valvetiming. VVT could be associated with VCT, or could be achieved byvarying the shape of the cam or the relationship of cam lobes to cam orvalve actuators to cam or valves, or by individually controlling thevalves themselves using electrical or hydraulic actuators. In otherwords, all VCT is VVT, but not all VVT is VCT.

The present invention provides a means to control a cam phaser. Thepresent invention is suitable for either a cam torque actuated phaser,TA phaser or oil pressure actuated phaser. By utilizing a center-mountedspool which is located rotationally to the housing as the control valve,the spool has two helical slots which serve to regulate the flow to theadvance and retard chambers. Axial displacement or translationalmovement of the spool allows either the advance or retard chambers tocommunicate with the common chamber such as common passage (62) of rotor(14). This results in the rotor displacing rotationally until the commonchamber no longer communicates with either the advance or retardchambers. At this point a new equilibrium rotational position for therotor relative to the housing/spool is reached. Displacements of therotor from the null position are counteracted by the common chambercommunicating to either the advance and retard chambers. Therefore therotational position is directly related to the axial position of thecenter spool.

The center spool can be positioned with or actuated upon by suchactuators as a variable force solenoid, step motor of by apressure/force balance (a pressure on one side of the spool reactingagainst a spring), etc.

Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments are not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

1. A phaser, comprising: a housing having at least one cavity therein; arotor having at least one vane oscillating within the at least onecavity of the housing, the rotor being disposed to engage the housing,or rotate relative to the housing, the cavity being divided into anadvance chamber and a retard chamber by the at least one vane; and acontrol valve disposed to translationally move within an opening of therotor along a substantially straight line, the control valve having atleast two openings for selectively controlling fluid flow among a set ofpassages within the phaser for control fluid to occupy either theadvance chamber or the retard chamber; at the outer surface of thecontrol valve, a helical slot having at least one side, wherein anon-zero angle exists between the at least one side and thesubstantially straight line, the helical slot having an opening forfacilitating fluid flow between chambers; thereby as the control valvemoves along the substantially straight line the vane position within thecavity is controlled.
 2. The phaser of claim 1, wherein the vane has avane cavity disposed to have at least one check valve placed therein. 3.The phaser of claim 1 further comprises means for limiting the controlvalve to move along the substantially straight line.
 4. The phaser ofclaim 1 further comprising a sprocket rigidly affixed to the housing anddisposed to rotate in unison with the housing.
 5. The phaser of claim 1further comprising a back plate rigidly affixed onto the housing androtor for containing control fluid within the phaser.
 6. A methodcomprising the steps of: providing a housing having at least one cavitytherein; providing a rotor having at least one vane oscillating withinthe at least one cavity of the housing, the rotor being disposed toengage the housing, or rotate relative the housing, the cavity beingdivided into an advance chamber and a retard chamber by the at least onevane; providing a control valve disposed to translationally move withinan opening of the rotor along a substantially straight line, the controlvalve having at least two openings for selectively controlling fluidflow among a set of passages within the phaser for control fluid tooccupy either the advance chamber or the retard chamber; at the outersurface of the control valve, providing a helical slot having at leastone side, wherein a non-zero angle exists between the at least one sideand the substantially straight line, the helical slot having an openingfor facilitating fluid flow between chambers; and translationally movingthe control valve along the substantially straight line a predetermineddistance for controlling the position of the vane within the cavity ofthe housing.
 7. The method of claim 6, wherein the vane has a vanecavity disposed to have at least one check valve placed therein.
 8. Themethod of claim 6 further comprising the step of providing a means forlimiting the control valve to move along the substantially straightline.
 9. The method of claim 6 further comprising the step of providinga sprocket rigidly affixed to the housing and disposed to rotate inunison with the housing.
 10. The method of claim 6 further comprisingproviding a back plate rigidly affixed onto the housing and rotor forcontaining control fluid within the phaser.